1. Field of the Invention
This invention relates to an Fe-Cr-Al type implant alloy for medical treatment. The alloy of the invention is useful as an implant material for medical treatment such as orthopedic surgery and dental surgery.
2. Prior Art
The implant material for orthopedic surgery is required to have the following properties:
1. that the implant material should be free from dissolution and absorption; PA0 2. that the material should be excellent in corrosion resistance; PA0 3. that the material should be excellent in mechanical strength and stable in its property over a long period of time; PA0 4. that the material should be nonpoisonous and nonirritative; PA0 5. that the material should have good biocompatibility with the tissue of a living body around the material. Namely, the material should be excellent in adaptability with the tissue or in affinity with the living body. If the implant material is low in biocompatibility with the tissue, a fibrous tissue which blocks and isolates the material from coming into contact with the living body develops in the living body in contact with the implant material with the result that the connection between the material and the living body gets loosened and gives rise to various impediments.
this is an essential problem that should be grasped not only as a direct and local problem but also as a comprehensive problem; and
A Fe-Ni-Cr type austenite stainless steel is being used as a conventional implant material. This stainless steel is excellent in mechanical property but offers a problem yet to be solved such as affinity with the living body. In addition, the stainless steel is not always sufficient in stress corrosion cracking resistance, pitting corrosion resistance, crevice corrosion resistance, and other corrosion resisting properties, so that the use of the stainless steel is limited to a short period of time. In addition, the harmful effects on the human body of the dissolved metallic ions, especially nickel ion or the like are a problem.
In recent years, trial use has been made of a ceramic material. This has many advantages in that it is excellent in corrosion resistance, stable in a living body over a long time, nonpoisonous to the body and high in biocompatibility, therewith. But it has the great disadvantage that it is deficient in mechanical strength, especially deflection resistance.